1. Field of the Invention
The present invention relates to a cleaning liquid used in photolithography for stripping and dissolving a thick photoresist pattern, and a method for treating a substrate therewith. The cleaning liquid of the invention is suitably applied especially for the formation of a bump in the production of a semiconductor device, such as IC and LSI.
2. Description of Related Art
In recent years, with the highly integration of semiconductor devices such as IC and LSI and downsizing of chip size, it has been required to micronize metallic wirings and to align bumps (minute salient electrodes) having a height of 20 μm or more on a substrate with high precision as connection terminals. In future, in conformity to further downsizing of chip size, highly precision of metallic wirings and bumps will become further necessary.
The bump formation is carried out by, for example, providing a metallic thin film on a substrate, forming a thick photoresist pattern on the metallic thin film by photolithography technique, providing a conductive layer on the photoresist pattern-uncovered area (i.e., a metallic thin film-exposed area) of the substrate to form bumps, and then removing the photoresist pattern.
Since the photoresist pattern is formed thickly usually in a film thickness of about 10-150 μm, the photoresist to be used is preferred negative-working photoresist materials in view of resistance to plating, pattern shape property, etc. However, it is difficult in removing photoresist pattern made of the negative-working photoresist materials as compared with the one made of positive-working photoresist materials. Thus, it is much more difficult in removing a thickly formed photoresist pattern made of the negative-working photoresist materials.
Further, during the formation process of the thick photoresist pattern, it is inevitable the pattern is liable to cause deformation in its shape, such as collapse and deficiency, because of its heavy film thickness. In such a case, it is necessary to discontinue the subsequent process and to carry out a re-work by removing away the deformed photoresist pattern from the substrate on the way of the works and do over again the formation of the photoresist pattern process from the first.
In any case of the removal of the photoresist pattern after the bump formation or the removal of the photoresist pattern for the re-work, after the immersion of the substrate having thereon a thick photoresist pattern in a cleaning liquid tank and thereby stripping (falling down) the pattern from the substrate, it is required the stripped-away photoresist pattern (cured material) be rapidly and completely dissolved in the cleaning liquid tank. When the stripped-away photoresist pattern remains in the cleaning liquid tank in a state of being insufficiently dissolved, there is the fear of a re-adhesion of the remaining cured photoresist pattern to the substrate, or in a continuous processing, to the subsequent substrate to be treated, which cause the inefficiency of the production. The prevention of corrosion of the metallic thin film is also required. In addition, in forming a bump on the substrate, a degenerated film is possibly formed at the interface between the photoresist pattern and the bump. It is therefore necessary to prevent the formation of such a degenerated film and to prevent the bump from corrosion.
JP-A-08-301911 describes a radiation-sensitive resin composition as a pattern forming material for the use of a bump formation and discloses in paragraph Nos. [0032] and [0043] a mixture of a quaternary ammonium, dimethyl sulfoxide and water (specifically, a dimethyl sulfoxide solution of 0.5 mass % of tetramethylammonium hydroxide (containing 1.5 mass % of water)) as a stripping liquid for stripping a photo-cured pattern. However, this stripping liquid involves problems such that it takes a time to dissolve the photo-cured pattern that was stripped away from the substrate in the stripping liquid, and that the throughput is low.
JP-A-10-239865 describes a formulation containing specific amounts of dimethyl sulfoxide, 1,3-dimethyl-2-imidazolidinone, a tetraalkylammonium hydroxide, and water as a stripping liquid for stripping a negative-working photoresist for forming a bump. As is the case of JP-A-08-301911 above, JP-A-10-239865 also involves problems such that it takes a time to dissolve the photo-cured pattern that was stripped away from the substrate in the stripping liquid, and that the throughput is low. Further, the stripping solution in JP-A-10-239865 contains 1,3-dimethyl-2-imidazolidinone as an essential component. This compound causes discoloration or corrosion of Cu.
In the photolithographic field, JP-A-2001-324823, JP-A-07-028254, etc., disclose stripping liquids containing a quaternary ammonium hydroxide and a water-soluble organic solvent such as dimethyl sulfoxide. However, none of those describe at all the removability of the hardly removable photoresists that are suitably used for forming a thick pattern for the formation of a bump.